Andrew May Be Upgraded To Category 5

For months, experts at the National Hurricane Center have deliberated, agonized and pored over piles of technical data.

On Wednesday, they're expected to reveal whether Hurricane Andrew will be formally upgraded to a Category 5, the most powerful and destructive kind of storm.

Indications are that it will.

Although keeping their decision close to the vest, center officials have made no secret they have strong evidence, based on new technological data, that Andrew packed maximum sustained winds of more than 160 mph.

That would mean the monster storm, which crushed south Miami-Dade County on Aug. 24, 1992, easily surpassed the 156-mph threshold for a Category 5 on the Saffir-Simpson Scale.

Until now, Andrew's maximum sustained winds have been officially set at 145 mph with peak gusts to 175 mph, which would make it a strong Category 4.

But with the spotlight on Andrew's 10-year anniversary this Saturday, officials want to clarify the storm's strength to better explain the massive destruction it caused, about $40 billion in 2002 dollars.

The final say rests with a panel called the Best Track Committee, consisting of hurricane specialists and research scientists, who studied new and historic data and listened to the arguments of other key experts.

Most agree Andrew's winds were more than 160 mph while the system was over Atlantic in the hours before landfall -- and remained potent for the first hour after the eye rolled ashore.

Herbert Saffir, a structural engineer who helped develop the Saffir-Simpson Scale, said Monday, "based on the structural damage I saw after Andrew, I would say there was sufficient damage to back up a Category 5."

On the other hand, Mark Powell, a research scientist and leading authority on Andrew's winds, has said he thinks the system ground down on the shoals and waves in Biscayne Bay in the hour before landfall.

His argument might have swayed the Best Track Committee to retain Andrew as a Category 4. Because the panel has been cautious in reaching its conclusion, a news conference releasing its findings might not be held until Thursday, officials said.

Bob Sheets, director of the National Hurricane Center in August 1992, said Monday the original estimate of Andrew's winds was conservative and he agrees the storm deserves Category 5 status.

He said the 145-mph wind speed was determined based on the amount of damage the storm caused in addition to some surface readings.

However, there were no credible readings because all wind-measuring instruments in the path of Andrew's core were destroyed, he said.

The decision whether to upgrade Andrew comes while the tropics remain calm -- but at a time when hurricane officials ask residents to be particularly vigilant and prepared for the worst.

The period from mid-August through October is considered the meanest part of the hurricane season, which runs through Nov. 30. More than 80 percent of the hurricanes documented since 1866 have formed in August, September and October.

So far, the 2002 season has seen three tame tropical storms, which is normal for this date, forecasters said. However, the first hurricane normally forms by Aug. 14.

To keep their records accurate, the Best Track Committee has made thousands of adjustments to tropical storm and hurricane tracks and wind speeds.

The committee looked into Andrew a decade later because of new data from small radar probes called GPS dropwindsondes, which were not available in 1992. In the past five years, the devices have been dropped from aircraft in and around the core of the most powerful storms, feeding back data on wind speed, direction, pressure and temperature.

In turn, they allowed scientists to determine the strength of hurricane winds at various levels. Researchers found that a hurricane's surface winds are usually 90 percent of the wind speed recorded at about 10,000 feet, the altitude that hurricane hunter airplanes penetrate a storm's eye wall.

In Andrew, surveillance planes recorded winds of 186 mph at upper levels, which would have placed the surface winds at about 165 mph. Prior to Andrew, only two Category 5 hurricanes had made landfall in the United States.